Looptaker drive mechanism for chainstitch sewing machines



United States Patent [72] Inventor I-lelmut Gross Kaiserslautern Pfalz, Germany [21] Appl. No. 806,158 [22] Filed March 1 1, 1969 [45] Patented Nov. 10, 1970 [73] Assignee G. M. Pfafl'A G Kaiserslautern Pfalz, Germany a corporation of Germany [32] Priority March 20, 1968 [33] Germany [31 1 31,128

[54] LOOPTAKER DRIVE MECHANISM FOR CHAINSTI'ICII SEWING MACHINES 8 Claims, 4 Drawing Figs.

[52] US. Cl 112/200 [51] D05b 1/06 [50] Field of Search I 12/200, 159, 197, 213

[56] References Cited UNITED STATES PATENTS 1,510,633 10/1924 Seymour 1 12/213ux 1,915,923 6/1933 Clayton.... 112/200 1,919,852 7/1933 Lutz; 112/159 Primary Examiner-Alfred R. Guest Attarneyl(arl Rath ABSTRACT: In a chainstitch sewing machine having a looptaker moving along an elliptical operating path during a stitchforming cycle, drive mechanism to produce component oscillating movements of the looptaker at right angle and parallel, respectively, to the stitching direction, comprises a first carrier rotatively mounted upon the frame of the machine about an axis being at right angle to the stitching direction, and a second carrier supporting said looptaker and rotatively mounted upon said first carrier about an axis parallel to the stitching direction. The first carrier is oscillated via first motion-transmitting and conversion means operably connecting the same with the drive shaft of the machine and the second carrier is oscillated via second motion-transmitting and conversion means operably connecting the same with said shaft and including a double-arm lever pivoted upon said first carrier and having an input arm forming part of the respective motion transmitting means and an output arm forming a knuckle joint together with a link connecting the same to a point of said second carrier.

Sheet I NV INT-OR.

H51. Mur (1-209! flAlQL RAT ATT ENE) Patented Nbv.10, 1970 Q 3,538,870

Sheet 3 of 2 I N V IFNTOR.

HELMt/T 4-90 BY LOOPTAKER DRIVE MECHANISM FOR CHAINSTITCII SEWING MACHINES The present invention relates to chainstitch sewing machines of the type having a hook or looptaker moving along an elliptical operating path composed of a lengthwise needle loop-seizing and shedding oscillating component at right angle to the stitching direction and a crosswise needle-avoid oscillating component parallel to the stitching direction, to produce chainstitches incooperation with a reciprocatory needle in the work being operated on. t

The invention is more particularly concerned with looptaker operating devices of the general type operated from the main drive shaft of the sewing machine, wherein a looptaker carrier is oscillated in the crosswise or needle-avoid coordinate direction via a first motion-transmitting and conversion mechanism operably connecting said carrier with the drive shaft, on the one hand, and wherein said carrier is simultaneously oscillated in the lengthwise or needle loop-seizing and shedding coordinate direction of said path via a second motion-transmitting and conversion mechanism operably connecting said carrier with said shaft, on the other hand, said second motion-transmitting mechanism including a doublearm intermediate connecting lever having an arm thereof linked to said looptaker carrier.

Looptaker operating devices of the foregoing type are especially suited for use in conjunction with sewing machines having a plurality of juxtaposed stitching needles cooperating with a single looptaker common to all the needles. The provision of a special link for the application of the lengthwise looptaker movements from the respective motion-transmitting means including an eccentric upon the drive shaft makes it possible, provided a suitable design of the transmitting mechanism, to operate the looptaker in such a manner as to accelerate its movement for the safe and ready seizing of the needle thread loop at the beginning of the looptaker operating cycle, on the one hand, and to decelerate or delay the looptaker at the end of its loop seizing movement until after the needle or needles have safely penetrated the triangle formed by the needle thread loop and looptaker threads, on the other hand. This operation, while rendering it possible to provide a close difference between the adjusting heights or positions of the me dies in the case of a multiple needle machine, has the further advantages of ensuring a safe and positive penetration of the thread triangle by the needles.

An important object of the present invention is the provision of motion-transmitting and operating mechanism for a looptaker of the referred to type designed to assume a relatively high initial velocity for the ready and safe seizing of the needle thread loop or loops, on the one hand, and to decelerate or retard the looptaker at the end of its needle thread-seizing movement, whereby to enable the needle or needles to safely penetrate the thread triangle, on the other hand, said mechanism being both simple in design and characterized by the use of a minimum of oscillating parts as well as relatively short motion-transmitting paths between the driving eccentrics upon the main drive shaft of the machine and the carrier supporting the looptaker, whereby in turn to enable the employment of relatively high sewing speeds without interfering with or impairing the stitch-forming operation.

The invention, bothas to the foregoing and ancillary objects as well as novel aspects thereof, will be better understood from the following detailed description, taken in conjunction with the accompanying drawings forming part of this disclosure and in which;

FIG. 1 is a front view of a chainstitch sewing machine embodying the improved looptaker drive mechanism constructed in accordance with the principle of the invention;

FIG. 2 is a perspective view of the improved drive mechanism embodied in FIG. 1;

FIG. 3 is a front view of the drive mechanism of FIG. 2, shown in the starting position of a looptaker operating path; and

FIG. 4 is a view similar to FIG. 3 and showing the device in the end position of the loop-seizing movement of the looptaker.

Like reference numerals denote like parts in the different views ofthe drawings.

With the foregoing object in view, the invention involves essentially the provision of motion-transmitting mechanism for the operation of a chainstitch looptaker of the referred to type, wherein a first carrier supporting the looptaker and the intermediate lever of the transmitting mechanism are both rotatively mounted upon a second carrier which serves to impart needle-avoid movements to the looptaker via the first carrier, and wherein the link connecting the output arm of said lever with said first carrier forms a knuckle joint with said arm. This results in a most simple and effective operating mechanism for the looptaker requiring a minimum of mounting space. Moreover, with said mechanism being designed or adjusted such as to cause said joint to move slightly beyond the stretched position of said arm and link at the instant of the looptaker reaching the end of its loop-seizing movement, the looptaker movement is sufficiently decelerated or retarded, to ensure a reliable and positive penetration of the thread triangle by the needle or needles, respectively, of the sewing machine.

According to an improved feature of the invention, the input arm of the intermediate lever is constructed for adjustment of its effective length, to adapt the machine to varying operating conditions or requirements. An especially simple embodiment for the adjustment of the effective length of said arm consists in the use of a releasable clamping device to secure the arm in varying relative positions to the associated motion-transmitting and conversion mechanism, in a manner as will become further apparent as the description proceeds in reference to the drawings.

Referring more particularly to FIG. I, the numeral 1 denotes the frame or housing of a conventional sewing machine comprising a cloth plate, an upright and an overhanging arm and within which are mounted the main drive shaft 2 of the machine, the needle rockshaft 3 connected with the needle frame 4 through a crank 5, the drive shaft 6 of the looptaker, and the rockshaft 9 supporting the carrier 7 of a work feed dog 8 of conventional construction. The looptaker drive shaft 6 is operably connected with the main drive shaft 2, carrying a hand wheel 10, via a chain belt 11 and chainwheels 12 and 13 fast upon the shafts 2 and 6, respectively.

Rockshaft 9 is operated by shaft 6 via an eccentric stitch controller 14 mounted upon shaft 6 and a link connection 15, whereby to impart to the shaft 9 oscillating or rocking movements which are in turn applied, to the feed dog 8 via the carrier 7, on the one hand, and to the crank 5 of the needle frame 4 via a link 16 and the needle rockshaft 3, on the other hand.

Mounted upon the frame 4 is a needle bar 17 which carries, in the example shown, three needles I8 for the sewing of a multiple cross-connected chainstitch scam in the work being operated on, in a manner well known. The needle bar 17 is vertically reciprocated in the frame 4 by the main drive shaft 2 via a conventional crank and link connection 19, 20.

While the sewing machine shown and described in the foregoing is equipped with both lower and upper feed devices, that is, the feed dog 8 and oscillating needle frame 4, it will become evident that a single feed may be employed without affecting the improvement and operation according to the in vention.

Adjustably secured to the front end of the looptaker drive shaft 6, FIG. 2, is an eccentric 21 which serves to produce the needle-avoid oscillating component of the looptaker movement, said eccentric being embraced by an eccentric arm 22 the free end of which is linked to an arm or extension 23 of a first carrier member 24 rotatively mounted upon the frame of the sewing machine about an axis being at right angle to the stitching direction or parallel to the lengthwise oscillating component of the looptaker operating path, respectively. For this purpose, the carrier 24 is rotatively mounted, in the example shown, upon a shaft 25 extending from a support 26 forming part of a bracket 27 upon the frame 1 of the sewing machine. Carrier 24 is secured against axial displacement upon theshaft 25 by means of a locking ring 28.

Further mounted upon the looptaker drive shaft 6 is a spur gear 29 which meshes with a similar gear 3h, FIGS. 2-4l, mounted upon a shaft 31 being parallel to the shaft 6 and journaled in the frame or bracket 27. The front end of shaft 31 carries a further eccentric 32 which serves to produce the needle loop-seizing and shedding oscillating component of the looptaker, eccentric 32. being embraced by the section 33 of a linked pull bar 34 the cooperating section 35 of which is linked with section 33 and embraces the spherical end of a connecting rod 36 forming a ball joint together with the link or section 35. Rod 36 of the ball joint is adjustably mounted in a bore of the split input arm 37 of an intermediate angular connecting lever 38 and secured in position by means of a nut to. The intermediate lever 38 which has an upwardly extending output arm 39 is rotatively supported upon the carrier 24 by a pin 4-2 connected to a fork-shaped extension 31 of said carrier.

The output arm 39 of the intermediate lever 38 is connected, via a relatively short link 43, with a second carrier 46 supporting the looptaker 47 and being in turn rotatively mounted upon the first carrier 24, about an axis parallel to the stitching direction, by means of a pin 45 secured in a forkshaped extension 44 of the carrier 24. The looptaker 47 supported by the carrier 43 cooperates in a known manner with the needles Hi, to produce a multiple cross-connected chainstitch scam in the work being operated on.

The link 43 and output arm 39 of the intermediate lever 3% together form a knuckle joint for the production of a nonuniform oscillating movement of the looptaker 47 in the loopseizing and shedding directions derived from the eccentric 32. Superimposed upon this movement is the oscillating component at right angle thereto or in the direction of the needleavoid component of the looper movement derived from the eccentric 211, to result composite elliptical path or movement of the looptaker during a stitch-forming operation or cycle of the sewing machine.

In operation, rotation, via the wheel 10, of the shaft 2 by the driving motor (not shown) of the sewing machine causes the needle bar i7 and needles 18 to be reciprocated in the vertical direction via the crank 19 and link 2h. At the same time, the looper drive shaft 6 and shaft 311 are driven via the chain belt ll and the gear pair 2?, 3h, respectively. As a consequence, oscillating movement is imparted, via the eccentric stitch controller l4 and link connection 15, to the rockshaft 9, and applied to the carrier '7 of the feed dog fill. Besides, oscillating movements are simultaneously applied, via the link 16, to the rockshaft 3 and transmitted, via the crank 5, to the needle frame 4, to cause a synchronous intermittent feed of the work both by the feed dog 3 and the needles 1%, in a manner well known with sewing machines equipped with both lower and upper feed devices.

The looptaker 4/7, being supported by the carrier 46 and cooperating with the needles 18 to produce multiple chainstitches in the work operated on, has applied to it, via link 34$, lever 38 and link 33, lengthwise loop-seizing and shedding movements derived from the eccentric 32 upon which are superimposed the crosswise or needle-avoid movements derived from the eccentric 232 via the eccentric arm 22 and oscillating carrier 2 which latter rotatively supports both the looptaker carrier 36 and the intermediate connecting lever 38.

By a suitable design of the knuckle joint formed by the link 43) and the driven or output arm 39 of the intermediate lever 33, the looptaker has imparted to it a relatively high initial velocity upon leaving the starting position, H6. 3, whereby to ensure a ready and safe seizure of the needle thread loop or loops, respectively. This in turn enables the height or position of the needles 718 to be adjusted to relative-close distances, while at the same time preventing a collapse" of the loop or loops prior to being penetrated or seized by the looptaker.

At the end of the loop-seizing movements of the looptaker, that is, upon reaching of its extreme point of the elliptical operating path 455, FIG. 3, the link 43 and lever arm 39 assume their stretched position, in which case the movement of the looptaker 47 is practically equal to zero. Where the link 3 and arm 39 pass beyond the stretched position of FKG. d, the looptaker 37 performs an oscillation about said point, in such a manner as to retard or delay the looptaker movement at the end of the loop-seizing movement until after the looptaker is subjected to its crosswise or needle-avoid movement derived from the eccentric 2i. and the needles i8 have been able to safely penetrate the thread triangle at points adjoining the respective loops, whereupon return of the looptaker to its starting position, FIG. 3, is initiated at a relatively low velocity. The varying velocities of the looptaker depend upon the design of the knuckle joint, that is, the maximum angle enclosed by the link 453 and lever arm 3?.

The extent of the oscillating movement of the looptaker may be varied by adjusting the relative position of the balljointed arm or link 36 and the input arm 37 of the lever 3% that is, varying the effective length of the arm 39. This enables a control of the looptaker operating path 423, to adapt the machine to varying operating conditions or requirements, such as stitching length, needle size, type of thread, etc.

In the known looptaker operating devices referred to hereinabove, the intermediate lever operably connected with the eccentric upon the main drive shaft serving to produce the lengthwise looptaker movements, on the one hand, and with the looptaker-carrier via a connecting link, on the other hand, is rotatjvely mounted upon the frame of the machine about an axis spaced at a relatively great distance from the locptaker carrier. inasmuch as the looptaker carrier is rotatively supported by the carrier subject to the needle-avoid movements, while the intermediate lever is rotatively supported about a stationary axis upon the frame of the machine, the link connecting both parts must be an equalizing connection, such for instance in the form of a ball-jointed arm or link.

Due to the relatively great distance between the axes of the looptaker carrier and the intermediate lever, the known looptaker operating devices require a considerabie mounting space for their operating parts. Besides, the transmission parts between the driving eccentric and the looptaker carrier and, in turn, the oscillating masses of the mechanism are such as to make it impossible to operate the machine so equipped at the high speeds required in practice, without affecting or impairing the stitch formation.

On the other hand, in the case of the improved looptaker drive mechanism according to the present invention, the mounting of the looptaker carrier 46 and intermediate lever 3% upon the same member, that is, the carrier 2d oscillating in accordance with the needle-avoid movements of the looptaker, results in relatively short transmission paths and reduced dimensions of the transmission parts or elements. As

a consequence, no disturbing oscillations result even at relatively high sewing speeds when using driving mechanism according to the invention. This in turn forestalls any impairment of or interference with the stitch formation. The reliability of the stitch formation is further increased by the looptaker 47 being practically at standstill or zero speed at the instant of penetration of the needles 1% into the thread triangles. Besides, as already pointed out, adjustment of the effective length of the lever arm 3'7 makes it possible in a most simple and efiicient manner to adapt the drive mechanism for use with varying stitch-forming and other operating conditions or requirements.

I claim:

1. In a chainstitch sewing machine having a frame, a drive shaft mounted in said frame, a reciproeatory needle, a threadcarrying looptaker, and drive mechanism to operate said looptaker over an elliptical path in synchronism with said needle, to sew chainstitches in a workpiece being operated on, said elliptical operating path being composed of lengthwise needle loop-seizing and shedding component movements at right angle to the stitching direction and crosswise needle-avoid component movements parallel to the stitching direction, the improvement consisting in said drive mechanism comprising:

i. a first carrier rotatively mounted upon said frame;

2. first motion-transmitting and conversion means operably connecting said carrier with said drive shaft, to impart periodic oscillating movements to said carrier;

3. a second carrier supporting said looptaker;

4. means rotatively supporting said second carrier by said first carrier, to impart needle-avoid component movements to said looptaker by said first carrier;

5. a two-arm angular intermediate lever having an input arm and an output arm and pivotally mounted upon said first carrier about an axis being at right angle to the axis of said first carrier;

6. second motion-transmitting and conversion means operably connecting said input arm with said drive shaft, to impart oscillating movements to said lever; and

7. a link connecting said output arm with an intermediate point of said second carrier, to impart loop-seizing and shedding component movements to said looptaker.

2. In a chainstitch sewing machine as claimed in claim 1, including means to adjust the effective length of the input arm of said lever.

3. In a chainstitch sewing machine as claimed in claim 1, said second motion-transmitting means including a balljointed link having its free end adjustably secured to said input arm, to vary the effective length of said arm.

4. in a chainstitch sewing machine as claimed in claim 3, wherein said ball-jointed link is slidably connected in a bore of the slit input arm of said lever, and releasable locking means securing said link and arm.

5. In a chainstitch sewing machine as claimed in claim 1, wherein said output arm and link form a knuckle joint designed to pass slightly beyond its stretched position at the end of the loop-seizing and beginning of the loop-shedding movements within said looptaker operating path.

6. In a chainstitch sewing machine having a frame, a drive shaft mounted upon said frame, a reciprocatory needle operable connected with said shaft, a looptaker cooperating with said needle, and drive mechanism to operate said looptaker along an elliptical operating path in synchronism with said needle, to sew chainstitches in a workpiece being operated on, said elliptical path being composed of a lengthwise needle loop-seizing and shedding oscillating component at right angle to the stitching direction and a crosswise needle-avoid oscillating component parallel to the stitching direction, the improvement consisting in said drive mechanism comprising:

1. a first carrier rotatively mounted upon said frame about an axis being at right angle to the stitching direction;

2. a second carrier supporting said looptaker and rotatively supported by said first carrier about an axis parallel to the stitching direction;

3. first motion-transmitting and conversion means operably connecting said first carrier with said shaft, to cause said first carrier to oscillate and to thereby impart needleavoid component movements to said looptaker;

4. a two-arm intermediate lever having an input arm and an output arm and rotatively mounted upon said first carrier about an axis parallel to the stitching direction;

5. a link connecting said output arm with a point of said second carrier, to provide a knuckle joint by said arm and link; and

6. second motion-transmitting means operably connecting said input arm with said shaft, to oscillate said lever and to impart loop-seizing and shedding component movements to said looptaker.

7. in a chainstitch sewing machine as claimed in claim 6, including means to adjust the effective length of the input arm of said lever.

8. In a chainstitch sewing machine as claimed in claim 6, said knuckle joint designed to slightly exceed the stretched position of its link and arm at the end of the loop-seizing and the beginning of the loop-shedding movements within said looptaker operating path. 

